Problem: Luis starts counting at 28, and he counts by threes. If 28 is the 1st number that Luis counts. what is the 12th number that he counts?
What is the first number that he counts? $28$ What is the second number that he counts? $\begin{align*}&28 + 3 \\ &= 31\end{align*}$ What is the third number that he counts? $\begin{align*}&28 + 3 + 3 \\ &= 28 + (2 \times 3) \\ &= 34\end{align*}$ What is the 12th number that he counts? $\begin{align*}&28 + (11\times3) \\ &= 28 + 33 \\ &= 61\end{align*}$